CVE-2026-39820: Go standard library net/mail · Inefficient Algorithmic Complexity
Affects Go standard library net/mailSource CVE Database V5
Not known to be exploited · CVSS 7.5 High : upgrade to 1.26.3 or 1.25.10 soon.
Data as of 30 Oct 2026, 11:52 UTC
- EPSS
- 0.7% chance of exploitation in 30 days – higher than 55% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 1.26.3, 1.25.10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 7 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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 30 Oct 2026.
What to do
Upgrade Go standard library net/mail to 1.26.3 or 1.25.10.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Go standard librarynet/mail | Affected
| Fixed in
|
| Go standard librarynet/mail | Affected
| Fixed in
|
Gonet/mailpkg:golang/net/mailOther threats | Affected
| Fixed in– |
Gonet/mailpkg:golang/net/mailOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
In the meantime, mitigating exposure by limiting or validating untrusted inputs to the affected functions may reduce risk, although no specific mitigation is officially recommended.
Description
Well-crafted inputs reaching ParseAddress, ParseAddressList, and ParseDate were able to trigger excessive CPU exhaustion and memory allocations.
References
- go.dev/issue/78566 (opens in a new tab)
- go.dev/cl/759940 (opens in a new tab)
- groups.google.com/g/golang-announce/c/qcCIEXso47M (opens in a new tab)
- pkg.go.dev/vuln/GO-2026-4986 (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-39820 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2467820 (opens in a new tab)
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39820.json (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:47952 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:34364 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:43692 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:36319 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:36625 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:36754 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:33574 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:23262 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:23264 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:41928 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:43038 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:42644 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:33120 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:33123 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:33142 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:33150 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:42146 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:43052 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:42796 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:41066 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:41031 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:40262 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:36797 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:50300 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:50205 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:50843 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:51033 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:54287 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:54285 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:54283 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:54284 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:54286 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:54274 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:54531 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:56340 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:54583 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:54602 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:54552 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:54883 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:54555 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:57194 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:57845 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:57914 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:49702 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:22120 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:22112 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:57649 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:49712 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:22121 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:59467 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:56789 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:56852 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:57482 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:57401 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:56854 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:57487 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:60520 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:61253 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:62407 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:62406 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:62260 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:63022 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:62754 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:62753 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:62803 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:59833 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:59830 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:60018 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:60023 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:65335 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:65534 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:65116 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:65336 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:65886 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:65117 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:65153 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:66327 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:65895 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:66016 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:51112 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:66022 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:50319 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:50336 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:67517 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:68334 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:65838 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:67974 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:68504 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:68527 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:67975 (opens in a new tab)