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Public proof of conceptFix available

CVE-2026-1525

A public proof of concept exists; no exploitation attested.

  • Published2026-03-12
  • Fixed in7.24.0 · 6.24.0
  • WeaknessCWE-444

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Undici allows duplicate HTTP Content-Length headers when they are provided in an array with case-variant names (e.g., Content-Length and content-length). This produces malformed HTTP/1.1 requests with multiple conflicting Content-Length values on the wire. Who is impacted: * Applications using undici.request(), undici.Client, or similar low-level APIs with headers passed as flat arrays * Applications that accept user-controlled header names without case-normalization Potential consequences: * Denial of Service: Strict HTTP parsers (proxies, servers) will reject requests with duplicate Content-Length headers (400 Bad Request) * HTTP Request Smuggling: In deployments where an intermediary and backend interpret duplicate headers inconsistently (e.g., one uses the first value, the other uses the last), this can enable request smuggling attacks leading to ACL bypass, cache poisoning, or credential hijacking

Timeline

dates in UTC
  1. 2026-03-1220:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-1525?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-1525?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV
Nodejs undici
BranchAffectedFixed in
7.x≥ 7.0.0, < 7.24.07.24.0
6.24< 6.24.06.24.0

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • nodejsAlmaLinux:9all versions · fixed in 1:24.14.1-2.module_el9.7.0+222+ef1c61e1and 4 other packages
  • nodejsAlmaLinux:8all versions · fixed in 1:22.22.2-1.module_el8.10.0+4158+e796f37fand 4 other packages
  • nodejsAlmaLinux:8all versions · fixed in 1:24.14.1-2.module_el8.10.0+4160+4819ac42and 4 other packages
  • nodejs-docsAlmaLinux:10all versions · fixed in 1:22.22.2-1.el10_1
  • nodejs-nodemonAlmaLinux:9all versions · fixed in 3.0.3-3.module_el9.7.0+209+ecf6523e
  • nodejs-nodemonAlmaLinux:8all versions · fixed in 3.0.1-1.module_el8.10.0+4006+3c416519
  • nodejs-nodemonAlmaLinux:8all versions · fixed in 3.0.3-1.module_el8.10.0+4061+f8ceeab9
  • nodejs-packagingAlmaLinux:9all versions · fixed in 2021.06-6.module_el9.7.0+209+ecf6523e

11 more package ranges on OSV.dev

Vendor advisories

  • RHSA-2026:56431 Red Hat Product Security68 products fixed

    Red Hat Security Advisory: Red Hat OpenShift Data Foundation 4.18.27 security, enhancement & bug fix update

  • RHSA-2026:21772 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: Red Hat OpenShift Dev Spaces 3.28.0 Release.

  • RHSA-2026:17789 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: Red Hat build of Cryostat 4.2.0: new RHEL 9 container image security update

  • RHSA-2026:13826 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat Developer Hub 1.9.4 release.

  • RHSA-2026:9742 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat Developer Hub 1.8.6 release.

  • RHSA-2026:7983 Red Hat Product Security43 products fixed

    Red Hat Security Advisory: nodejs:22 security update

7 more advisories

Full record on NVD

Fix

  1. Update Nodejs undici to 7.24.0 · 6.24.0
  2. Vendor fix Red Hat Product Security RHSA-2026:56431 · 68 productsBefore applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://docs.redhat.com/en/documentation/red_hat_openshift_data_foundation/4.18/html/updating_openshift_data_foundation/updating-ocs-…
  3. Vendor fix Red Hat Product Security RHSA-2026:21772 · 4 productsBefore applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
  4. Vendor fix Red Hat Product Security RHSA-2026:17789 · 4 productsYou can download the Cryostat 4 on RHEL 9 container images that this update provides from the Red Hat Container Registry at registry.access.redhat.com. Installation instructions for your platform are available in the Red Hat Container Catalog (see the References section). Dockerfiles and scripts s…
  5. Vendor fix Red Hat Product Security RHSA-2026:13826 · 1 productFor more about Red Hat Developer Hub, see References links
  6. Vendor fix Red Hat Product Security RHSA-2026:7983 · 43 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
  7. Workaround from the vendor Red Hat Product Security RHSA-2026:56431 · 81 productsMitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • CISA-ADPSSVC decisionpoc2026-03-12
  • OpenCVESSVC decisionpoc—
  • CNACVSS 3.16.5read 2026-10-23
  • NVDCVSS 3.19.8read 2026-10-23
  • CNAweakness (CWE)CWE-444read 2026-10-23
  • FIRST EPSSEPSS score0.5 %2026-10-22
  • OSVaffected packages—

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2026-03-12
Last Modified
2026-06-17
NVD status
Analyzed

Frequently asked questions

What is CVE-2026-1525?

Undici allows duplicate HTTP Content-Length headers when they are provided in an array with case-variant names (e.g., Content-Length and content-length). This produces malformed HTTP/1.1 requests with multiple conflicting Content-Length values on the wire. Who is impacted: * Applications using undici.request(), undici.Client, or similar low-level APIs with headers passed as flat arrays * Applications that accept user-controlled header names without case-normalization Potential consequences: * Denial of Service: Strict HTTP parsers (proxies, servers) will reject requests with duplicate Content-Length headers (400 Bad Request) * HTTP Request Smuggling: In deployments where an intermediary and backend interpret duplicate headers inconsistently (e.g., one uses the first value, the other uses the last), this can enable request smuggling attacks leading to ACL bypass, cache poisoning, or credential hijacking

Is CVE-2026-1525 actively exploited?

A proof-of-concept exploit exists for CVE-2026-1525, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2026-1525?

CVE-2026-1525 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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