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High 2 vendors · 2 advisories

CVE-2026-116270: MIME::Words versions before 5.521 for Perl allow memory exhaustion via repeated "=?" sequences in decode_mimewords

CVE-2026-116270 key facts

CISA KEV
Not listed (catalogue checked )
Highest advisory rating
High
CVSS base score
7.5 (Red Hat)
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H · base score 7.5, scored by CISA-ADPAttack vector: network. Attack complexity: low. Privileges required: none. User interaction: none. Scope: unchanged. Confidentiality impact: none. Integrity impact: none. Availability impact: high.
Weakness
  • CWE-407 Inefficient Algorithmic Complexity
CISA SSVC
Exploitation: none observed. Automatable: yes. Technical impact: partial. CISA, .
Vendor advisories
2 from Proxmox, Red Hat
Assigned by
CPANSec (CNA)
CVE record published
Listed by VulniPulse
Record changed

Ratings, versions and fixes are quoted from the vendor advisories that cover only CVE-2026-116270; each belongs to its advisory, not to every product listed. How records are collected and checked.

Description

MIME::Words versions before 5.521 for Perl allow memory exhaustion via repeated "=?" sequences in decode_mimewords. For each "=?" that does not start a complete encoded word, decode_mimewords appends an error message containing the whole input string to $@. A boundary of 8,000 "=?" pairs (16,000 bytes) adds 8,000 copies of itself to $@, about 128 MB. From version 5.518, MIME::Parser decodes every multipart boundary this way, so a remote sender can exhaust the memory of the parsing process with one Content-Type header.

Text from the CVE.org record (CPANSec).

How do I fix CVE-2026-116270?

  • Upgrade to MIME-tools 5.521 or later. (CVE.org record)

Vendor advisories for CVE-2026-116270

Proxmox

1 advisory
  • Advisory severityUnrated

    Advisory [CVE-2026-116264 +9] Proxmox Mail Gateway: Several issues in libmime-tools-perl

    PSA-2026-00091Source published

    This bulletin covers 10 CVEs. The products, versions, score and guidance below describe the bulletin; check its source for applicability to this specific CVE.

    The MIME::Tools package is used for parsing mails in Proxmox Mail Gateway. Recently two new releases for MIME::Tools were released upstream, fixing several issues, including 10, which were assigned CVE identifiers. The issues can result in bypassing certain mail-filter rules similar to issues PSA-2026-00005-1 and PSA-2026-00049-1. Additionally parsing certain messages could result in spending an excessive amount of CPU time by pmg-smtp-filter. PMG used the Max files setting of the Virus detector as general limit on the maximal number of parts in a mail since at least version 5.0. This effectively limited the effect of the unlimited CPU time. The fixes for the issues were backported and are available in version 5.515-1+pmg3 of libmime-tools-perl. Additionally a hard-coded limit on the…

    Affected products in this advisory
    • Proxmox Mail Gateway
    Source-reported affected versions
    Affected-version details not available in this record.
    Source-reported fixed versions
    • libmime-tools-perl 5.515-1+pmg3
    • pmg-api 9.1.5
    Mitigation guidance
    • Update to the fixed package versions: libmime-tools-perl >= 5.515-1+pmg3, pmg-api >= 9.1.5.
    Full advisory and evidenceOpen source bulletin

Red Hat

1 advisory
  • Advisory severityHigh7.5

    High [CVE-2026-116270] Denial of Service via memory exhaustion from crafted MIME headers

    CVE-2026-116270Source published Source updated

    Denial of Service via memory exhaustion from crafted MIME headers. Red Hat rates this important (CVSS 7.5). Weakness: CWE-770. Affected products named by the advisory: Red Hat Enterprise Linux 6; Red Hat package: perl-mime-tools.

    Related products — impact not confirmed
    • Red Hat Enterprise Linux 6
    • Red Hat package: perl-mime-tools
    Source-reported affected versions
    • < 5.521
    Source-reported fixed versions
    No fixed-version detail extracted. This does not mean no fix exists.
    Mitigation guidance
    No mitigation guidance extracted; consult the source.
    Full advisory and evidenceOpen source bulletin

References

Timeline

  1. CVE record published
  2. First vendor advisory listed by VulniPulse
  3. CVE record last updated

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