CVE-2026-27857
Description
Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer commands will result in client disconnection. This 1 MB can be left allocated for longer time periods by not sending the command ending LF. So attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Install fixed version, there is no other remediation. No publicly available exploits are known.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
OS impact
SUSE Affected 1 release
| Version | Status | Fixed in |
|---|---|---|
| — | Affected | — |
AlmaLinux Fixed 1 release
| Version | Status | Fixed in |
|---|---|---|
| 9 | Fixed | dovecot-pigeonhole-2.3.16-15.el9_7.1.aarch64.rpm |
Debian Fixed 5 releases
| Version | Status | Fixed in |
|---|---|---|
| trixie | Fixed | 1:2.4.1+dfsg1-6+deb13u4 |
| sid | Fixed | 1:2.4.3+dfsg1-1 |
| forky | Fixed | 1:2.4.3+dfsg1-1 |
| bullseye | Fixed | 1:2.3.13+dfsg1-2+deb11u3 |
| bookworm | Fixed | 1:2.3.19.1+dfsg1-2.1+deb12u2 |
Red Hat Fixed 2 releases
| Version | Status | Fixed in |
|---|---|---|
| 9 | Fixed | — |
| 8 | Fixed | — |
Rocky Linux Fixed 1 release
| Version | Status | Fixed in |
|---|---|---|
| 9 | Fixed | — |
References
- https://access.redhat.com/errata/RHSA-2026:13857
- https://access.redhat.com/errata/RHSA-2026:19364
- https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json
- https://security-tracker.debian.org/tracker/CVE-2026-27857
- https://www.suse.com/security/cve/CVE-2026-27857.html
- https://access.redhat.com/errata/RHSA-2026:13830
- https://bugzilla.redhat.com/2452172
- https://bugzilla.redhat.com/2452175
- https://bugzilla.redhat.com/2452179
- https://errata.almalinux.org/8/ALSA-2026-13830.html
- https://errata.almalinux.org/9/ALSA-2026-13857.html
- https://errata.almalinux.org/9/ALSA-2026-19364.html
- https://errata.rockylinux.org/RLSA-2026:13857
CWEs
CWE-400
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.