# CVE-2026-106554: jackson-dataformat-cbor: quadratic-time TagList growth on unbounded stacked tags (CPU/GC DoS, PoC)

Status: published. Published: 2026-11-04. Updated: 2026-11-04.

One CBOR-parsing issue in jackson-dataformats-binary's CBOR module: an unbounded run of CBOR tags drives quadratic-time TagList growth (CPU/GC-exhaustion DoS, PoC-proven).



PoC executed against com.fasterxml.jackson.dataformat:jackson-dataformat-cbor:2.18.2; present in current 2.x and 3.x (tools.jackson.dataformat.cbor) HEAD. Distinct from the Avro and Smile/Protobuf advisories for this repo.



Quadratic CPU/GC DoS from an unbounded chain of CBOR tags (PoC-proven). File: cbor/src/main/java/.../cbor/CBORParser.java (tag handling -> TagList).



CBOR permits a data item to be preceded by any number of semantic tags. The CBOR parser accumulates them in a TagList whose backing array grows by a fixed increment (+8), not by doubling, and re-scans/copies on each growth. An attacker sends a value preceded by a long run of tag bytes; the fixed-increment growth makes accumulating N tags O(N^2) in time (plus GC pressure), with no cap on the number of stacked tags.



PoC (executed, JDK 17): feeding a CBOR stream consisting of a long run of tag bytes (e.g. tag 0xC0+) before a trivial value forces quadratic CPU/GC; parse time grows super-linearly with the tag count, pinning a request thread with no configurable limit.



Impact. Algorithmic-complexity denial of service (CWE-407): a modest input of stacked tags consumes quadratic CPU/GC, pinning a request thread; concurrent requests exhaust the pool.



Fix. Grow TagList by doubling and/or cap the number of stacked tags (StreamReadConstraints-style).

## Remediation

No remediation reported in collected sources

## Affected products and versions

- FasterXML / jackson-dataformat-cbor (com.fasterxml.jackson.dataformat:jackson-dataformat-cbor): ≥ 2.15.0; < 2.18.12 (affected, maven); 2.18.12 (unaffected, maven); ≥ 2.19.0; < 2.21.8 (affected, maven); 2.21.8 (unaffected, maven); ≥ 2.22.0; < 2.22.4 (affected, maven); 2.22.4 (unaffected, maven). Source: CNA: HeroDevs
- FasterXML / jackson-dataformat-cbor (tools.jackson.dataformat:jackson-dataformat-cbor): ≥ 3.0.0; < 3.1.8 (affected, maven); 3.1.8 (unaffected, maven); ≥ 3.2.0; < 3.2.4 (affected, maven); 3.2.4 (unaffected, maven). Source: CNA: HeroDevs

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-407

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/FasterXML/jackson-dataformats-binary/security/advisories/GHSA-cjg7-h3pr-p927 (CNA: HeroDevs; vendor-advisory)

- https://github.com/FasterXML/jackson-dataformats-binary/security/advisories/GHSA-cjg7-h3pr-p927 (36c7be3b-2937-45df-85ea-ca7133ea542c)

## Provenance

- CNA: HeroDevs: https://www.cve.org/CVERecord?id=CVE-2026-106554; retrieved 2026-11-04; source updated 2026-11-04

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-106554; retrieved 2026-11-04; source updated 2026-11-04

Revision: fa8294ad9a25338e089cda36f6277bd867a93c74ea9ff710bb31b34921e6d054

Canonical: https://y2.dev/cve/CVE-2026-106554

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