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VulnerabilityPublished Updated

CVE-2026-86409: curl · Setting CURLOPT_AWS_SIGV4 to NULL but does not disable SigV4 authentication, contrary to expectations

Affects curlSource GCVE Database

0
Authoritative record:CVE-2026-86409· High

Not known to be exploited · fixed in 7.81.0-1ubuntu1.30 : patch curl soon.

Data as of 28 Oct 2026, 22:28 UTC

Severity
High

Rated by Threat Radar · CVSS not yet scored by NVD

Patch
Available – fixed in 7.81.0-1ubuntu1.30, 8.5.0-2ubuntu10.16, 8.20.0-2ubuntu11.1 +1

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 20 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
Ubuntu 26.10curlpkg:deb/ubuntu/curl?arch=source&distro=stonkingOther threatsAffected
  • <8.20.0-2ubuntu11.1
Fixed in
  • 8.20.0-2ubuntu11.1
Ubuntu 26.04 LTScurlpkg:deb/ubuntu/curl?arch=source&distro=resoluteOther threatsAffected
  • <8.18.0-1ubuntu2.8
Fixed in
  • 8.18.0-1ubuntu2.8
Ubuntu 24.04 LTScurlpkg:deb/ubuntu/curl?arch=source&distro=nobleOther threatsAffected
  • <8.5.0-2ubuntu10.16
Fixed in
  • 8.5.0-2ubuntu10.16
Ubuntu 22.04 LTScurlpkg:deb/ubuntu/curl?arch=source&distro=jammyOther threatsAffected
  • <7.81.0-1ubuntu1.30
Fixed in
  • 7.81.0-1ubuntu1.30

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

Setting `CURLOPT_AWS_SIGV4` to NULL but does not disable SigV4 authentication, contrary to expectations and documentation. A subsequent transfer on the same handle still sends an `Authorization: AWS4-HMAC-SHA256` header to whatever URL isset next, leaking state information.

References

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