# CVE-2026-81869: OpenTelemetry-Go: UTF-8 replacement rune bypasses attribute length truncation > Attackers can bypass attribute length limits in OpenTelemetry-Go by using Unicode replacement characters, causing excessive memory consumption and potential denial of service. - **Severity:** Medium 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`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 16 Sep 2026 - **Updated:** 17 Sep 2026 - **Also known as:** AZL-103073, AZL-103131, AZL-103143, AZL-103149, AZL-103155, AZL-103161, AZL-103170, AZL-103179, AZL-103191, AZL-103221, AZL-103233, AZL-103239, AZL-103245, AZL-103248, AZL-103257, DEBIAN-CVE-2026-81869, ECHO-86a3-f4f3-560d, GHSA-p9f8-wvj8-2fg8, GO-2026-6616, MINI-22j5-pjw7-mpf9, MINI-22p2-2w8h-f2cv, MINI-26rx-hv4q-c3r8, MINI-27h3-83wj-8jx5, MINI-2f9g-4m2j-6r46, MINI-2xpw-2fj9-9m46, MINI-35j6-6mwh-qrjw, MINI-37cp-64fx-29p2, MINI-3p9h-r852-8j7m, MINI-3qwf-v5fj-h32p, MINI-3wjr-4442-fjf9, MINI-42jp-3pqc-63v5, MINI-445m-f89f-ch4m, MINI-47p3-x874-h5qw, MINI-4mh6-2p63-p4v6, MINI-4pcm-3h3j-3p89, MINI-577c-hqhw-wcwj, MINI-579w-8fw9-x759, MINI-57m6-38c7-w34x, MINI-59rf-554c-3fqh, MINI-5f6h-vhpc-vm59, MINI-5q5j-72x5-rq57, MINI-5rg3-qv9x-rh94, MINI-5x48-7xj2-87g4, MINI-6657-gmwv-vg34, MINI-66p4-9667-x68g, MINI-6hwv-9chg-9h9h, MINI-6jx9-g5px-m46p, MINI-6mxg-v2xx-7f8r, MINI-6vxr-936q-fv3g, MINI-735w-3qjh-qcjx, MINI-792h-q4v5-436p, MINI-797m-fj23-m6m8, MINI-7p5p-vf2g-rjw6, MINI-7r6v-8jf4-469p, MINI-7ww7-cwh3-2f2r, MINI-829c-8m6w-59rq, MINI-832f-w4g5-98v4, MINI-8728-f3wr-chrf, MINI-8xxw-jqfw-95m3, MINI-948h-g35v-f752, MINI-99h8-9w88-cfpm, MINI-9fwv-pmp8-fx84, MINI-9hgv-xj76-hf37, MINI-9j4h-fgf8-mr3j, MINI-9p36-xpc7-8p78, MINI-c372-x523-vr38, MINI-c4w8-283g-hh75, MINI-c9xm-p8vq-f7x8, MINI-cmp4-39ww-q5r6, MINI-cq24-jr9r-g6x9, MINI-crc9-ffqc-78hg, MINI-crwr-65fm-99vm, MINI-cw2x-rgfm-jh3q, MINI-cwmx-xvvf-vmjp, MINI-f497-xq62-247x, MINI-f52j-cjwm-gqjf, MINI-ffgg-qqwv-24cp, MINI-fj35-cq2c-hxfr, MINI-fjm9-wfc2-wjq6, MINI-fpvm-cfmm-84xq, MINI-fxwp-53gp-qhpq, MINI-g2rf-ff2p-j3vr, MINI-g7qw-8rhp-vr6v, MINI-gjqm-5gf2-qq27, MINI-grq8-qpxg-822m, MINI-h465-6574-592v, MINI-h62p-4c7j-8pfv, MINI-h69c-qpg3-cxwm, MINI-h858-8v8f-p339, MINI-hhf6-hj56-w79q, MINI-hvwp-p4hx-wh7f, MINI-j2wq-8p9r-gjvp, MINI-j48f-rqg7-jrqh, MINI-jcfh-h8fv-hjg4, MINI-jrgw-mj96-9rf8, MINI-jxjj-7447-gr69, MINI-m2rq-xv49-hvp8, MINI-mcrm-4w6x-pq7r, MINI-mgpv-g2xv-x7gc, MINI-mjh7-58v7-j825, MINI-mrc9-2v6p-4f4x, MINI-mxmx-7q8j-rg36, MINI-pcr3-3v58-xgqj, MINI-prxv-23m4-3qj7, MINI-pwqx-5pwr-4vqj, MINI-q463-8774-xgp4, MINI-q726-hxgm-68jm, MINI-qh22-g2j2-5cqr, MINI-qhrr-9pwj-72xq, MINI-r3wj-qxvh-j7cq, MINI-r886-pq3j-w35g, MINI-v283-hj73-7fhg, MINI-vp76-gvf9-v7w5, MINI-vv5f-5hq2-rcv6, MINI-w4g5-j3rj-fxf8, MINI-w532-4873-8jf4, MINI-w589-mhmw-2j4m, MINI-w62x-46wj-mh28, MINI-w928-8v5f-wpj2, MINI-wr7f-frgr-xm3j, MINI-x3jr-9jj3-68h6, MINI-x5jh-gpww-fmxc, MINI-x8rh-h2j7-62x2, MINI-x9h9-6c94-6rhj, MINI-xh4f-hp44-247q, MINI-xmp7-9h65-cpxj, MINI-xmr9-5m4j-xgpw, MINI-xpq6-rw7r-hx6x, MINI-xqfp-rfxh-2855, MINI-xqg8-php4-62cf, UBUNTU-CVE-2026-81869 ## What is CVE-2026-81869? CVE-2026-81869 is a medium-severity denial of service vulnerability in open-telemetry opentelemetry-go, published on 16 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description 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. Weakness: CWE-400 (Uncontrolled Resource Consumption), CWE-176 (Improper Handling of Unicode Encoding) ## Which versions are affected by CVE-2026-81869? 3 open source packages ship an affected version, including go.opentelemetry.io/otel/sdk. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `go.opentelemetry.io/otel/sdk` | Go | From 1.10.0 | 1.33.0 | | `go.opentelemetry.io/otel/sdk` | Go | From 1.10.0 | 1.33.0 | | `go.opentelemetry.io/otel/sdk` | Go | From 1.10.0 | 1.33.0 | ## How do I fix CVE-2026-81869? Upgrade go.opentelemetry.io/otel/sdk to 1.33.0 or later. ## Is CVE-2026-81869 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-81869 exists. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-81869 and fix it if it is affected. What it is: CVE-2026-81869 is a medium-severity denial of service vulnerability in open-telemetry opentelemetry-go, published on 16 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-81869 exists. Affected packages and fixed versions: - go.opentelemetry.io/otel/sdk (Go): affected from 1.10.0; fixed in 1.33.0 - go.opentelemetry.io/otel/sdk (Go): affected from 1.10.0; fixed in 1.33.0 - go.opentelemetry.io/otel/sdk (Go): affected from 1.10.0; fixed in 1.33.0 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-81869/ (Markdown: https://insights.sbomify.com/CVE-2026-81869/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-81869 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-81869 - OSV: https://osv.dev/vulnerability/CVE-2026-81869 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-81869/ Summaries are generated and may contain mistakes; the official description above is the record.