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NVD injury continued |

NVD injury continued |

2023-06-13 07:31:03

There’s something about having your product put in in over twenty billion situations everywhere in the world and even out of the globe. In my case it helps me stay centered on and dedicated to engaged on the safety elements of curl. Ideally, we’ll by no means have our heartbleed second.

Safety can also be a typically rising concern on this planet round us and Open Supply safety maybe particularly so. That is one purpose why NVD making things up is such a giant drawback.

The Nationwide Vulnerability Database (NVD) has a world presence. They host and share details about safety vulnerabilities. If you seek for a CVE Id utilizing your favourite search engine, it’s seemingly that the primary outcome you get is a hyperlink to NVD’s web page with details about that particular CVE. They take it upon themselves to coach the world about safety points. A job that definitely is required but in addition one which places a accountability and requirement on them to be correct. Once they get issues improper. they assist distributing misinformation. Misinformation makes folks doubtlessly draw the improper conclusions or act in improper, incomplete or exaggerated methods.

Low or Medium severity points

There are well-known, acknowledged and respected Open Supply tasks who by coverage by no means problem CVEs for safety vulnerabilities they rank severity low or medium. (I cannot establish such tasks right here as a result of it’s not the purpose of this put up.)

Such a coverage efficiently avoids the danger that NVD will vastly inflate their points since they will already solely be excessive or vital. However is it serving to the customers and the ecosystem at giant?

Within the curl mission we’ve got a coverage which makes us register a CVE for each single reported or self-detected drawback that may have a safety influence. Both at will or by mistake. This features a honest quantity of low and medium points. The quantity of low and medium points as a complete of all points will increase over time as we hold discovering points, however the actually dangerous ones are much less often reported.

As we’ve got all knowledge recorded and saved, we are able to visualize this growth over time. Under is a graph exhibiting the curl vulnerability and severity degree developments since 2010.

Severity distribution in reported curl vulnerabilities since 2010

Out of the 145 revealed curl safety vulnerabilities to date, 28% have been rated severity excessive or vital whereas 104 of them have been set low or medium by the curl safety crew.

I believe this development is simple to elucidate. It’s due to two separate developments:

  1. We as a mission have matured and have discovered over time learn how to take a look at higher, write code higher to reduce danger and we’ve got existed for some time to have a sequence of really dangerous flaws already discovered (and stuck). We make much less critical bugs today.
  2. Since 2010, a number of extra folks search for safety issues and today we’re significantly better higher at figuring out issues as safety associated and we’ve got higher instruments, whereas for just a few years in the past the identical drawback would simply have grow to be “a bug repair”.

Deciding severity

When a safety drawback is reported to curve, the curl safety crew and the reporter collaborate. First to ensure we perceive the total width of the issue and its safety influence. What can occur and what’s required for that badness to set off? Additional, we assess what the likeliness that this may be executed on objective or by mistake and the way frequent these conditions and required configurations may be. We all know curl, we all know the code however we additionally typically return and double-check precisely what the documentation says and guarantees to higher assess what customers needs to be anticipated to know and do, and what’s not anticipated from them and so forth. And we re-read the concerned code repeatedly.

curl is at the moment somewhat over 160,000 strains of function packed C code (excluding clean strains). It won’t all the time be straight ahead to an informal observer precisely how all the things is glued collectively even when we attempt to additionally document internals that will help you discover deeper data.

I believe it’s honest to say that it requires a specific amount of expertise and time spent with the code to have the ability to totally perceive a curl safety problem and what influence it might need. I consider it’s troublesome or subsequent to inconceivable for somebody with out data about the way it works to simply casually learn our safety advisories and attempt to second-guess our assessments and as an alternative make your personal.

But that is precisely what NVD does. They don’t even ask us for assist or for clarifications of something. They assume they will assess the severity of our issues with out figuring out curl nor totally understanding the reported points.

A case to show my level

In March 2023 we revealed a safety advisory for the issue generally known as CVE-2023-27536.

That is doubtlessly a safety drawback, in all probability by no means hurts anybody and is in reality fairly unlikely to ever trigger an issue. But it surely may. So after deliberating we accepted it and ranked it severity low.

Bear with me right here. I’ll spend two paragraphs revealing some particulars from the inner libcurl engine:

The issue is of a sort we’ve got had a number of occasions up to now: curl has a connection pool and when a person makes a subsequent request which this specific choice modified (in comparison with the way it was when the earlier connection was setup) it might wrongly reuse the primary connection considering they’d the very same properties.

The second would then unintentionally get the improper rights as a result of it was setup otherwise. Nonetheless, the primary connection would want the right credentials and all the things and so would the second, it might simply differ relying on what “GSSAPI delegation” that’s allowed.

NVD ranks this

The particular person or crew at NVD whose job it’s to make up stuff for safety vulnerabilities ranked this as CRITICAL 9.8. Nearly as dangerous because it will get apparently. 10 is the max as you may recall.

When realizing this, on the finish of Might, I first fell off my chair in shock by this madness, however after a fast restoration I emailed them (once more) and complained (but once more) on setting this severity for *27536. I used the phrase “ridiculous” in my e-mail to explain their actions. Why and who advantages from them scaremongering the world like this? It is senseless. Quite the opposite, that is dangerous for everybody.

As a response to my criticism, somebody at NVD went again and agreed to revise the CVSS string they’d set and abruptly it was “solely” ranked HIGH 7.2. I say “somebody” as a result of they by no means talk with names and by no means signal the emails which whomever I speak to. They’re simply “NVD”.

I objected to their new CVSS string as properly. It’s simply not a excessive severity safety drawback!

In my new argument I modified two specific particulars within the CVSS string (in comparison with the one they insisted was good) and offered arguments for that. In your pleasure, I embody my actual wording beneath. (Some emphasis is added right here for show functions.)

How I motivated a downgrade

I may probably stay with: AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N (4.4) - even when which means Medium and we argue Low.

These are two adjustments and my motivations:

Assault complexity excessive - as a result of how this requires that you just even have a working first communication after which do a second is barely modified and you'd count on the second to be totally different however in actuality it unintentionally reuse the primary connection and due to this fact provides totally different/elevated rights.

It's a super-niche and nearly inconceivable assault and there was no report ever of anybody having suffered from this and even the existence of an software that truly would allow it to occur.

It's extra prone to solely occur by mistake by an software, but it surely additionally appears unlikely to ever be utilized by an software in a means that will set off it since having the identical person credentials with totally different values for GSS delegation and assume totally different entry ranges appears … bizarre.

This nearly inconceivable probability of occurring is the first purpose we predict this can be a Low severity. With CVSS, it appears inconceivable to achieve Low.

Privileges Required excessive - as a result of the one means you'll be able to set off this flaw is by having full privileges for the *similar* person credentials that's later used once more however with modified GSS API delegation set. Whereas the earlier connection remains to be stay within the connection pool.

It might additionally solely be an assault or a flaw if that second switch really assumes to have totally different entry properties, which might be debatable if customers of the API would count on or not

CVSS nonetheless sucks

CVSS is a crap system so utilizing this single-dimension quantity it appears subsequent to inconceivable to truly get severity low report.

NVD desires “public sources”

NVD doesn’t simply take my phrase for the way curl works. I imply, I solely wrote a big chunk of it and am in all probability the one human that is aware of most about its internals and the way it works. I additionally wrote the patch for this problem, I wrote the connection pool logic and I perceive the issue precisely. Nope, simply because I say so doesn’t make it true.

See Also

My claims above about this problem can in fact be verified by studying the publicly accessible supply code and you may run assessments to breed my claims. To not point out that the performance in query is documented.

However no.

They determined to comply with one in every of my proposed adjustments, which additional downgraded the severity to MEDIUM 5.9. Fairly far-off from their preliminary stance. I believe it’s not less than a partial victory.

For the second change to the CVSS string I requested, they demand that I present extra info for them. Of their phrases:

There is no such thing as a publicly accessible details about the CVE that clarifies your assertion so we should request clarification from you and moreover have this element added to the HackerOne report or another public interface for transparency functions prior to creating adjustments to the CVSS vector.

… which simply emphasizes precisely what I’ve acknowledged already on this put up. They set a severity on this with out understanding the problem, with no data of the function that will get this improper and with out clues about what is definitely essential to set off this flaw within the first place.

For folks intimately accustomed to curl internals, we really don’t must spell out all these details with excruciating particulars. We all know how the connection pool works, how the reuse of connections ought to work and what it means when curl will get it improper. We’ve additionally had a number of different points on this areas up to now. (It’s a difficult space to get proper.)

But it surely doesn’t make this CVE greater than a Low severity problem.


This problem is now caught at this MEDIUM 5.9 at NVD. A lot much less dangerous than the place they began. Probably Low or Medium doesn’t make an enormous distinction on the market on this planet.

I believe it’s outrageous that I must battle and argue for such a giant and famend group to do proper. I can’t do that for each CVE we’ve got reported as a result of it takes critical time and power, however on the similar time I’ve zero expectation of them getting this proper. I can solely assume that they’re equally misplaced and dangerous when assessing safety issues in different tasks as properly.

A very damaged and nugatory system. That individuals appear to truly use.

It’s definitely tempting to hitch the tasks that don’t report Low or Medium points in any respect. If we might cease doing that, not less than NVD wouldn’t shout wolf and foolishly declare they’re vital.

My response

That could be a ridiculous request.

I am stating *verifiable details* concerning the flaw and the way curl is susceptible to it. The publicly accessible info that is primarily based on is the precise supply code which is brazenly accessible. You may as well confirm my claims by operating code and checking what occurs and you then'd see that my statements match what the code does.

The truth that you assess the severity of this (and different) CVE with out understanding the fundamental details of the way it works and what the vulnerability is, simply emphasizes how futile your work is: it doesn't work. If you don't even hassle to determine this stuff out then in fact you can't set a wise severity degree or CVSS rating. Now I perceive your failures significantly better.

We within the curl mission's safety crew already know the way curl works, we perceive this vulnerability and we set the severity accordingly. We needn't restate recognized details. curl performance is properly documented and its supply code has all the time been open and public.

When you've got questions after having learn that, be happy to achieve out to the curl safety crew and we might help you. You attain us at

I like to recommend that you just (NVD) all the time speak to us earlier than you set CVSS scores for curl points in order that we might help information you thru them. I believe that would make the world a greater place and it might definitely profit a world of curl customers who belief the information you present.

 / Daniel

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