# CVE-2026-91777: jackson-databind: quadratic forward-reference completion in Collection and Map deserializers > Attackers can cause CPU exhaustion via quadratic complexity in jackson-databind deserialization of identity-enabled collections or maps. - **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 23 Sep 2026 - **Updated:** 23 Sep 2026 - **Also known as:** ALSA-2026:85231, CLEANSTART-2026-AJ37436, CLEANSTART-2026-BX50217, CLEANSTART-2026-DY58341, CLEANSTART-2026-EA40241, CLEANSTART-2026-GM79198, CLEANSTART-2026-JQ80765, CLEANSTART-2026-KZ87014, CLEANSTART-2026-NY89801, CLEANSTART-2026-OO80208, CLEANSTART-2026-PU63110, CLEANSTART-2026-VA82083, CLEANSTART-2026-WO73143, CLEANSTART-2026-XT22555, CLEANSTART-2026-YK30931, DEBIAN-CVE-2026-91777, ECHO-3b4b-f633-121f, GHSA-cxp5-3px4-pw24, MINI-22f8-45j9-5r3w, MINI-22xq-wpxc-rrr4, MINI-24jc-23gw-v39x, MINI-24qv-x6p3-xrw6, MINI-24wq-ccfj-6mvc, MINI-2f2p-9vg3-jjvh, MINI-2v79-9hw2-2c2f, MINI-2vjp-2437-cwg2, MINI-2wq3-q7cq-rmm3, MINI-322q-x79g-849h, MINI-34vx-p747-j5q3, MINI-35cc-c286-ch56, MINI-36f5-m8ff-3w45, MINI-3gv8-qhp8-xmm9, MINI-3pg8-6hh3-hfp8, MINI-3qhc-jfx7-x8vv, MINI-485c-wx6h-qmpw, MINI-4m42-9jw2-r338, MINI-4mfj-rpgj-8w7f, MINI-4pgh-q288-vjw6, MINI-52g6-656f-6h87, MINI-5rf7-7h2c-w978, MINI-66vm-cvqr-w29q, MINI-6vm2-gw3r-44x9, MINI-6xr4-f65x-6rrm, MINI-73vm-f4h2-6wq4, MINI-74c8-6793-q8jx, MINI-752g-wfw3-qv3w, MINI-76h8-92x2-6mcj, MINI-787j-8j2q-9573, MINI-78qx-gjwp-jr2c, MINI-7cxr-r8qc-657g, MINI-7jqw-6gj9-923v, MINI-7w5x-4fv6-fwc2, MINI-849v-wp33-vx57, MINI-8g7w-w558-gmrj, MINI-989x-gcm6-4rmj, MINI-9j56-wj9g-pvm7, MINI-9jc6-834q-hv5c, MINI-c2c3-6xx8-5mjx, MINI-c4r4-3pfm-xw45, MINI-c5vq-mq96-x5mv, MINI-c9mw-33ff-rpvj, MINI-chpw-f69f-qjgv, MINI-cqhx-8g7x-f78q, MINI-f678-rxj5-xgc3, MINI-f7h3-4qg9-2fcx, MINI-f947-5hr5-crgg, MINI-f95m-5cf7-4c43, MINI-fmfx-p38c-r6x9, MINI-gfq3-3f65-95gg, MINI-gj4c-3xvr-22pf, MINI-gp97-q8w8-xh26, MINI-gx2g-4wc2-3jvx, MINI-hgj6-5vxp-7cx3, MINI-j7fq-6jp2-jwv6, MINI-j864-fr9w-pc5r, MINI-j9fh-x5m5-vpmv, MINI-jc7x-33j4-wwmf, MINI-jjcq-63c4-cpwj, MINI-jq9h-hcx7-f8p3, MINI-jvf8-rw29-53pc, MINI-jww4-5xff-3285, MINI-m5h5-9hq2-8jv8, MINI-m96p-ghfq-96w2, MINI-m9v7-3v2r-h3qh, MINI-p7fc-c3hc-q4xf, MINI-pjrm-7xgr-277v, MINI-pmrv-gr6x-549w, MINI-pp9m-8r36-cqmq, MINI-pv8g-9jpc-rxrp, MINI-q54p-48vr-279m, MINI-qccx-9436-q774, MINI-qfx7-c6rj-39vv, MINI-qjcm-7pp2-w355, MINI-rh3g-h222-6rp2, MINI-v3j3-jc8h-hgrx, MINI-vqcf-pgxg-52f5, MINI-vrj8-hqj3-mq39, MINI-w482-6p7m-45x4, MINI-w6gf-gm7g-c8mh, MINI-w7q9-2p85-mw23, MINI-w95x-5mf7-2373, MINI-w9jq-2v73-747c, MINI-wv66-7m56-hmxx, MINI-wwjv-x3cr-c64p, MINI-x9g2-5pgw-5xx7, MINI-xc5r-87cm-q5hv, MINI-xcmv-p5x8-x96m, MINI-xhp3-9prp-qf3w, MINI-xx8q-7gv9-vx7f, RHSA-2026:85231, RLSA-2026:85231, ROOT-APP-MAVEN-CVE-2026-91777, UBUNTU-CVE-2026-91777 ## What is CVE-2026-91777? CVE-2026-91777 is a high-severity denial of service vulnerability in FasterXML jackson-databind, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description Forward-reference completion for @JsonIdentityInfo object IDs in FasterXML jackson-databind performs a linear scan of the pending-reference accumulator for every resolved ID. The affected paths are CollectionDeserializer.CollectionReferringAccumulator.resolveForwardReference() and the equivalent implementation in MapDeserializer. When a document first creates N unresolved object-ID references in an identity-enabled collection or map and then defines those same IDs in reverse order, completion performs on the order of N * (N + 1) / 2 identity comparisons, so a shallow document whose size grows linearly causes quadratic CPU work during deserialization. The reporter instrumented equals() calls on the ID class and measured exactly 2,003,000 comparisons at N = 2,000, against zero comparisons in the pending-reference lookup path for an equally sized control in which every reference was already resolved. The input requires no deep nesting and no syntactically unusual JSON. Exploitation requires an application that deserializes attacker-influenced JSON into an identity-enabled collection or map. The fix replaces the repeated linear lookup with a keyed pending-reference structure. Weakness: CWE-400 (Uncontrolled Resource Consumption) ## Which versions are affected by CVE-2026-91777? 10 open source packages ship an affected version, including com.fasterxml.jackson.core:jackson-databind and tools.jackson.core:jackson-databind. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `com.fasterxml.jackson.core:jackson-databind` | Maven | From 2.19.0 | 2.21.7 | | `com.fasterxml.jackson.core:jackson-databind` | Maven | From 2.19.0 | 2.21.7 | | `com.fasterxml.jackson.core:jackson-databind` | Maven | From 2.22.0 | 2.22.3 | | `com.fasterxml.jackson.core:jackson-databind` | Maven | From 2.22.0 | 2.22.3 | | `com.fasterxml.jackson.core:jackson-databind` | Maven | From 2.5.0 | 2.18.11 | | `com.fasterxml.jackson.core:jackson-databind` | Maven | From 2.5.0 | 2.18.11 | | `tools.jackson.core:jackson-databind` | Maven | From 3.0.0 | 3.1.7 | | `tools.jackson.core:jackson-databind` | Maven | From 3.0.0 | 3.1.7 | | `tools.jackson.core:jackson-databind` | Maven | From 3.2.0 | 3.2.3 | | `tools.jackson.core:jackson-databind` | Maven | From 3.2.0 | 3.2.3 | | `pki-jackson-databind` | AlmaLinux:9 | All versions | 2.21.6-1.el9_8.1 | | `jackson-databind` | Red Hat:enterprise_linux:9::appstream | All versions | 0:2.21.6-1.el9_8.1 | | `pki-jackson-databind` | Red Hat:enterprise_linux:9::appstream | All versions | 0:2.21.6-1.el9_8.1 | | `jackson-databind` | Rocky Linux:9 | All versions | 0:2.21.6-1.el9_8.1 | ## How do I fix CVE-2026-91777? Upgrade com.fasterxml.jackson.core:jackson-databind to a fixed version for your release line: 2.21.7, 2.22.3 or 2.18.11. ## Is CVE-2026-91777 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-91777 exists. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-91777 and fix it if it is affected. What it is: CVE-2026-91777 is a high-severity denial of service vulnerability in FasterXML jackson-databind, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-91777 exists. Affected packages and fixed versions: - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.19.0; fixed in 2.21.7 - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.19.0; fixed in 2.21.7 - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.22.0; fixed in 2.22.3 - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.22.0; fixed in 2.22.3 - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.5.0; fixed in 2.18.11 - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.5.0; fixed in 2.18.11 - tools.jackson.core:jackson-databind (Maven): affected from 3.0.0; fixed in 3.1.7 - tools.jackson.core:jackson-databind (Maven): affected from 3.0.0; fixed in 3.1.7 - tools.jackson.core:jackson-databind (Maven): affected from 3.2.0; fixed in 3.2.3 - tools.jackson.core:jackson-databind (Maven): affected from 3.2.0; fixed in 3.2.3 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-2026-91777/ (Markdown: https://insights.sbomify.com/CVE-2026-91777/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-91777 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-91777 - OSV: https://osv.dev/vulnerability/CVE-2026-91777 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-91777/ Summaries are generated and may contain mistakes; the official description above is the record.