# CVE-2026-91776: jackson-databind: unbounded growth of the type id cache in TypeDeserializerBase retains every unknown raw type ID > Attackers can cause memory exhaustion in jackson-databind by supplying unique unknown type IDs when name-based polymorphism with a fallback is enabled. - **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:** CLEANSTART-2026-AA74935, CLEANSTART-2026-AO45932, CLEANSTART-2026-AT75001, CLEANSTART-2026-AV92018, CLEANSTART-2026-JM36564, CLEANSTART-2026-MO11506, CLEANSTART-2026-OP95878, CLEANSTART-2026-OV27346, CLEANSTART-2026-OY78254, CLEANSTART-2026-VQ30141, CLEANSTART-2026-WW59813, CLEANSTART-2026-WX80544, CLEANSTART-2026-XV17458, DEBIAN-CVE-2026-91776, ECHO-8ef9-d35a-7067, GHSA-wv8q-qhhj-9h54, MINI-233x-98gj-q26p, MINI-298q-2vw2-gw4r, MINI-29vj-ff44-g874, MINI-2hjq-qmm3-vh65, MINI-2mpq-4qwr-qv95, MINI-2r5g-cxwc-xr37, MINI-2rj5-464h-73v8, MINI-3564-qp4r-j679, MINI-35r5-5rq9-9hqg, MINI-3j4c-wf8x-xhmp, MINI-3r75-r43f-phh8, MINI-3v33-pc5w-9qgg, MINI-3x6p-4885-vggj, MINI-46m3-4328-v57h, MINI-48r8-xq2q-w893, MINI-49xp-jwr2-jh95, MINI-4h85-99m2-74p5, MINI-4x82-83c8-5fww, MINI-529g-6mpm-3hh7, MINI-53x8-5rc4-9xwg, MINI-596p-qmr7-8vg7, MINI-59h8-cq2j-gjhg, MINI-5q3q-x7jj-hjr7, MINI-6832-8mq3-639w, MINI-6wm6-qw8g-55rh, MINI-73f4-9553-pfwj, MINI-7f2m-gxqf-g856, MINI-7hx3-9x5c-w4cj, MINI-7vwp-vvxq-4jvw, MINI-854v-7gqv-58jr, MINI-86p6-9743-p65p, MINI-8ccm-x2g7-vqp9, MINI-8f3p-qp5x-v3m8, MINI-8h2h-6xmh-7mmp, MINI-8qm9-m7wg-8449, MINI-8vv4-fqfp-5465, MINI-9wfp-r3j7-72hc, MINI-c3qg-r646-7wfm, MINI-chpq-7h9r-mjjm, MINI-cm97-w8hg-7qhg, MINI-cwjp-q49p-vw4f, MINI-f3f9-v97w-fv75, MINI-f3wm-cfhv-crxp, MINI-f82w-7rcf-pv79, MINI-f976-66cp-63wx, MINI-fhrm-3c5q-jpjh, MINI-g7g6-99c4-p66w, MINI-g7xr-wvgh-rw63, MINI-h2p4-r9vw-54q9, MINI-h634-83x6-g5hg, MINI-hff5-p74q-pr8r, MINI-hfgc-gcrj-f582, MINI-hqcx-j6c2-gjfq, MINI-hv2f-f352-vvxx, MINI-j6jx-h3w4-m395, MINI-jf68-9cm8-3gvj, MINI-jmjv-jv2f-jqc7, MINI-m4vh-97hg-xw9q, MINI-p2jw-89wp-3j2j, MINI-pf48-hh8q-wf5h, MINI-pg55-298q-xwjg, MINI-pm6p-8qv3-3jph, MINI-q324-xffj-f285, MINI-q553-hvqf-q99g, MINI-q8pp-wpcr-xq6q, MINI-qcj5-25mw-wqxh, MINI-qhcw-3mq8-f9qf, MINI-r25c-8r49-36f6, MINI-r72f-cc2c-9jxr, MINI-rfh4-3qcc-f76x, MINI-rfv3-754j-mg6g, MINI-rp79-rh89-mm9m, MINI-rp8m-h7mp-f6x5, MINI-rpxp-87h3-fwq4, MINI-rwwm-2qm4-cjj8, MINI-vcq2-wg28-8xpm, MINI-vhqm-2jjp-jhhq, MINI-w2vx-cx48-j7mh, MINI-w44p-wprv-8673, MINI-w583-8q3g-xrp7, MINI-w7rf-9hmp-6f56, MINI-w7rp-q9x9-9cw7, MINI-wg76-f74p-mfff, MINI-x32r-7qwr-6v3x, MINI-x66f-p6q6-qr9j, MINI-x896-345x-7mqr, MINI-xc8m-2crg-rp4r, MINI-xgq3-qc26-gq3m, MINI-xjhp-gf5h-c54v, MINI-xm2m-j985-rff8, MINI-xq37-f9g6-3q52, RHLW-2026-bcaf0a0ae0978229, ROOT-APP-MAVEN-CVE-2026-91776, UBUNTU-CVE-2026-91776 ## What is CVE-2026-91776? CVE-2026-91776 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 TypeDeserializerBase._findDeserializer() in FasterXML jackson-databind caches the resolved deserializer under the raw, attacker-supplied type ID. When name-based polymorphism is configured with a fallback, for example @JsonTypeInfo(use = Id.NAME, defaultImpl = ...), every distinct unrecognized type ID resolves to the same fallback deserializer but is retained as its own key in the _deserializers map. That map has no configurable bound and lives for the lifetime of the type deserializer, so an attacker who can repeatedly supply fresh unknown type IDs causes monotonic memory retention across requests. The reporter observed 10,000 retained entries from 10,000 distinct unknown IDs, against a single entry for a control that repeated one unknown ID the same number of times, isolating attacker-controlled key cardinality from request volume. Exploitation requires an application that enables name-based polymorphism with a defaultImpl or equivalent fallback, accepts attacker-influenced type IDs, and reuses a long-lived ObjectMapper across requests. The fix stops caching fallback resolutions for unrecognized IDs and bounds both the number of cached entries and the length of a cacheable type ID. Weakness: CWE-400 (Uncontrolled Resource Consumption) ## Which versions are affected by CVE-2026-91776? 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 2.0.0 | 2.18.11 | | `com.fasterxml.jackson.core:jackson-databind` | Maven | From 2.0.0 | 2.18.11 | | `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 | | `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 | ## How do I fix CVE-2026-91776? Upgrade com.fasterxml.jackson.core:jackson-databind to a fixed version for your release line: 2.18.11, 2.21.7 or 2.22.3. ## Is CVE-2026-91776 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-91776 exists. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-91776 and fix it if it is affected. What it is: CVE-2026-91776 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-2026-91776 exists. Affected packages and fixed versions: - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.0.0; fixed in 2.18.11 - com.fasterxml.jackson.core:jackson-databind (Maven): affected from 2.0.0; fixed in 2.18.11 - 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 - 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-2026-91776/ (Markdown: https://insights.sbomify.com/CVE-2026-91776/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-91776 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-91776 - OSV: https://osv.dev/vulnerability/CVE-2026-91776 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-91776/ Summaries are generated and may contain mistakes; the official description above is the record.