Skip to content
Fencer Intel
medium 5.1

CVE-2026-81869 json

OpenTelemetry-Go: UTF-8 replacement rune bypasses attribute length truncation

published last mo. modified last mo. also EUVD-2026-81260 , GHSA-p9f8-wvj8-2fg8 , GO-2026-6616

cvss
5.1
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 7%
public exploits
0
none known

Summary

OpenTelemetry-Go is the Go implementation of OpenTelemetry. From version 1.10.0 until 1.33.0, the sdk/trace/span.go attribute truncation path can fail to enforce AttributeValueLengthLimit for string and string-slice attributes containing the valid Unicode replacement character U+FFFD. safeTruncateValidUTF8 treats the valid replacement rune as invalid UTF-8 and returns the original input, while strings.ToValidUTF8 leaves that valid rune unchanged, so a second safeTruncate attempt can also return the oversized value. An attacker who controls span attribute content can retain values longer than the configured limit, increasing per-span memory use and weakening denial-of-service protection in the instrumented process. This issue is fixed in version 1.33.0.

Patch / fix

  • go go.opentelemetry.io/otel/sdk 1.33.0
  • linuxfoundation opentelemetry-go 1.33.0
  • opentelemetry opentelemetry 1.33.0
  • golang-opentelemetry-otel Debian 14 1.43.0-1

debian advisories DEBIAN-CVE-2026-81869

  • cert-manager Azure Linux 3.0 1.12.15-14
  • docker-compose Azure Linux 3.0 2.27.0-15
  • flannel Azure Linux 3.0 0.24.2-33
  • kube-vip-cloud-provider Azure Linux 3.0 0.0.10-10
  • moby-containerd-cc Azure Linux 3.0 1.7.7-18
  • moby-engine Azure Linux 3.0 25.0.18-1
  • opa Azure Linux 3.0 0.63.0-6

azure linux advisories AZL-103143AZL-103161AZL-103170AZL-103233AZL-103239AZL-103245

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Is CVE-2026-81869 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-81869 updated cvss 4.0

github.com/open-telemetry/opentelemetry-go: OpenTelemetry-Go: Denial of Service via attribute length truncation bypass

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
last mo.

Exploit prediction

0.18% chance of exploitation in the next 30 days, higher than 7% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/open-telemetry/opentelemetry-go/security/advisories/GHSA-p9f8-wvj8-2fg8 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 5.1 CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
CNA 4.0 5.1 CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
go go.opentelemetry.io/otel/sdk
>=1.10.0, <1.33.0
1.33.0

Affected products

  • open-telemetry opentelemetry-go

Classification

Weakness
  • CWE-176 Improper Handling of Unicode Encoding
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.