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CVE-2026-42504VulnerabilityPublished Updated

Red Hat Security Advisory: osbuild-composer security update

Affects Red Hat osbuild-composerSource GCVE Database

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Mentioned vulnerabilities

Authoritative record:CVE-2026-42504· High 7.5

Not known to be exploited · CVSS 7.5 High : upgrade Red Hat mime to 1.26.4 or 1.25.11 soon.

Data as of 30 Oct 2026, 02:31 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CISA-ADPCVSS 3.17.5
Patch
Available – fixed in 1.26.4, 1.25.11
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 2 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: 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 29 Oct 2026.

What to do

Upgrade mime to 1.26.4 or 1.25.11.

Affected software

ProductAffectedFixed in
Go standard librarymimeAffected
  • >=1.26.0-0 <1.26.4
Fixed in
  • 1.26.4
Go standard librarymimeAffected
  • <1.25.11
Fixed in
  • 1.25.11
Gomimepkg:golang/mimeOther threatsAffected
  • <1.25.11
  • >=1.26.0-0 <1.26.4
Fixed in
  • 1.25.11
  • 1.26.4

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

Description

A service for building customized OS artifacts, such as VM images and OSTree commits, that uses osbuild under the hood. Besides building images for local usage, it can also upload images directly to cloud. It is compatible with composer-cli and cockpit-composer clients. Security Fix(es): * mime: golang: Golang MIME: Denial of Service via maliciously-crafted MIME header (CVE-2026-42504) * google.golang.org/grpc: gRPC-Go: Denial of Service via malformed RPC requests (CVE-2026-84445) * net/http: golang: golang: Denial of Service via crafted HTTP Range headers (CVE-2026-78667) * crypto/tls: golang: crypto/tls: Denial of Service via multiple ECH outer extension references (CVE-2026-97031) * net/textproto: mime/multipart: golang: golang: Denial of Service via memory limit bypass in multipart form parsing (CVE-2026-94440) * net/http: net/http/internal/http2: golang.org/x/net/http2: net/http: Denial of Service via excessive HTTP/2 SETTINGS frames (CVE-2026-78669) * crypto/x509: golang: crypto/x509: Man-in-the-middle attacks via untrusted intermediate certificates (CVE-2026-111943) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

References

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