opentelemetry-go: AttributeValueLengthLimit is fully bypassed by attribute values composed of valid U+FFFD runes

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

• CVE-2026-128085: 0.47% estimated exploitation activity in the next 30 days; percentile 41.12 (FIRST EPSS, 2026-11-14). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The `AttributeValueLengthLimit` span/log-record limit can be bypassed entirely with attribute values that consist of valid U+FFFD (REPLACEMENT CHARACTER) runes. The counting-based truncation introduced by the fix for GHSA-p9f8-wvj8-2fg8 (commit `e016a78c9`, first released in v1.33.0) has an "optimistic" fast path that skips every U+FFFD without counting it and without falling back to the correct slow path. A value of 1000 U+FFFD runes (3000 bytes) is stored verbatim even with a limit of 5 characters (15 bytes). The same defect affects the attribute truncation paths in `go.opentelemetry.io/otel/sdk/trace` (`sdk/internal/attrnorm`), `go.opentelemetry.io/otel/sdk/log` (`sdk/log/internal/attrnorm`), and the auto-instrumentation tracer in `go.opentelemetry.io/otel/trace` (`trace/auto.go`, introduced in `v1.35.0`). This is an incomplete-fix issue: it is a distinct defect in the replacement code that GHSA-p9f8-wvj8-2fg8 introduced, affecting exactly the versions that advisory…

Published by the source

13 Nov 2026, 19:00 UTC

Last modified by the source

13 Nov 2026, 19:15 UTC

Source last checked

14 Nov 2026, 08:05 UTC

1. Revision 2 · amended · 14 Nov 2026

   Amended from osv record GHSA-q7gw-24fr-5p69

2. Revision 1 · created · 13 Nov 2026

   Published from ghsa record GHSA-q7gw-24fr-5p69

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# Patch Next advisory brief: CVE-2026-128085

Advisory: opentelemetry-go: AttributeValueLengthLimit is fully bypassed by attribute values composed of valid U+FFFD runes
IDs: CVE-2026-128085, GHSA-q7gw-24fr-5p69
Record: https://patchnext.com/advisories/cve-2026-128085 (revision 2, source checked 14 Nov 2026, 08:05 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: go.opentelemetry.io/otel/sdk/log 1.47.0; go.opentelemetry.io/otel/sdk 1.47.0; go.opentelemetry.io/otel/trace 1.47.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go go.opentelemetry.io/otel/sdk/log: affected >= 0.9.0, < 1.47.0; fixed in 1.47.0
- Go go.opentelemetry.io/otel/sdk: affected >= 1.33.0, < 1.47.0; fixed in 1.47.0
- Go go.opentelemetry.io/otel/trace: affected >= 1.35.0, < 1.47.0; fixed in 1.47.0

## Suggested inspection (read-only)
- Go go.opentelemetry.io/otel/sdk/log: check the installed version with your package manager.
- Go go.opentelemetry.io/otel/sdk: check the installed version with your package manager.
- Go go.opentelemetry.io/otel/trace: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on go.opentelemetry.io/otel/sdk/log, go.opentelemetry.io/otel/sdk, go.opentelemetry.io/otel/trace.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-q7gw-24fr-5p69 (GitHub-reviewed advisory GHSA-q7gw-24fr-5p69 lists affected ranges: Go go.opentelemetry.io/otel/sdk >=1.33.0 =0.9.0 =1.35.0 <1.47.0)
- Verified: https://osv.dev/vulnerability/GHSA-q7gw-24fr-5p69 (OSV record GHSA-q7gw-24fr-5p69 lists affected ranges: Go go.opentelemetry.io/otel/sdk >=1.33.0 =0.9.0 =1.35.0 <1.47.0 (fixed))

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