diff --git a/Dockerfile b/Dockerfile
index 2af6f55..baf352d 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -9,10 +9,9 @@ FROM debian:${DEBIAN_VERSION} as terraform
 ARG TARGETARCH
 ARG TERRAFORM_VERSION
 RUN apt-get update
-# RUN apt-get install --no-install-recommends -y libcurl4=7.74.0-1.3+deb11u7
-RUN apt-get install --no-install-recommends -y ca-certificates=20230311
-RUN apt-get install --no-install-recommends -y curl=7.88.1-10+deb12u4
-RUN apt-get install --no-install-recommends -y gnupg=2.2.40-1.1
+RUN apt-get install --no-install-recommends -y ca-certificates=20230311+deb12u1
+RUN apt-get install --no-install-recommends -y curl=7.88.1-10+deb12u14
+RUN apt-get install --no-install-recommends -y gnupg=2.2.40-1.1+deb12u2
 RUN apt-get install --no-install-recommends -y unzip=6.0-28
 WORKDIR /workspace
 RUN curl --silent --show-error --fail --remote-name https://releases.hashicorp.com/terraform/${TERRAFORM_VERSION}/terraform_${TERRAFORM_VERSION}_linux_${TARGETARCH}.zip
@@ -27,12 +26,12 @@ RUN unzip -j terraform_${TERRAFORM_VERSION}_linux_${TARGETARCH}.zip
 FROM debian:${DEBIAN_VERSION} as aws-cli
 ARG AWS_CLI_VERSION
 RUN apt-get update
-RUN apt-get install -y --no-install-recommends ca-certificates=20230311
-RUN apt-get install -y --no-install-recommends curl=7.88.1-10+deb12u4
-RUN apt-get install -y --no-install-recommends gnupg=2.2.40-1.1
+RUN apt-get install -y --no-install-recommends ca-certificates=20230311+deb12u1
+RUN apt-get install -y --no-install-recommends curl=7.88.1-10+deb12u14
+RUN apt-get install -y --no-install-recommends gnupg=2.2.40-1.1+deb12u2
 RUN apt-get install -y --no-install-recommends unzip=6.0-28
-RUN apt-get install -y --no-install-recommends git=1:2.39.2-1.1
-RUN apt-get install -y --no-install-recommends jq=1.6-2.1
+RUN apt-get install -y --no-install-recommends git=1:2.39.5-0+deb12u3
+RUN apt-get install -y --no-install-recommends jq=1.6-2.1+deb12u1
 WORKDIR /workspace
 RUN curl --show-error --fail --output "awscliv2.zip" --remote-name "https://awscli.amazonaws.com/awscli-exe-linux-x86_64-${AWS_CLI_VERSION}.zip"
 COPY security/awscliv2.asc ./
@@ -47,10 +46,10 @@ FROM debian:${DEBIAN_VERSION} as build
 LABEL maintainer="bgauduch@github"
 RUN apt-get update \
   && apt-get install -y --no-install-recommends \
-    ca-certificates=20230311\
-    git=1:2.39.2-1.1 \
-    jq=1.6-2.1 \
-    openssh-client=1:9.2p1-2+deb12u1 \
+    ca-certificates=20230311+deb12u1 \
+    git=1:2.39.5-0+deb12u3 \
+    jq=1.6-2.1+deb12u1 \
+    openssh-client=1:9.2p1-2+deb12u10 \
   && apt-get clean \
   && rm -rf /var/lib/apt/lists/*
 WORKDIR /workspace
diff --git a/docs/adr/0010-apt-package-pinning-strategy.md b/docs/adr/0010-apt-package-pinning-strategy.md
new file mode 100644
index 0000000..6002269
--- /dev/null
+++ b/docs/adr/0010-apt-package-pinning-strategy.md
@@ -0,0 +1,65 @@
+# 0010 — APT package pinning strategy
+
+- Status: Accepted
+- Date: 2026-06-15
+- Deciders: @bgauduch
+
+## Context and problem statement
+
+The Dockerfile pins every OS package to an exact version
+(`ca-certificates=20230311+deb12u1`, `curl=7.88.1-10+deb12u14`, …). Debian
+removes superseded point-release versions from the `bookworm` mirror, so a stale
+pin eventually disappears and the build fails with `apt-get … exit code 100`.
+This broke `build-test` (the pin `ca-certificates=20230311` had been superseded
+by `…+deb12u1`). The question is whether to keep pinning, drop pins, or freeze
+the mirror.
+
+## Decision drivers
+
+- Reproducibility and supply-chain integrity of the image.
+- Predictable, reviewable dependency changes.
+- Acceptable maintenance for a low-traffic project.
+
+## Considered options
+
+- **Keep exact version pins** and refresh them when Debian supersedes a version
+  (or on base-image bumps).
+- **Unpin** the OS utility packages (rely on the stable suite). *Rejected — loses
+  reproducibility and makes dependency changes invisible.*
+- **`snapshot.debian.org`** as a frozen apt source so exact pins never disappear.
+
+## Decision outcome
+
+Chosen option: **keep exact version pins** for all OS packages
+(`ca-certificates`, `curl`, `gnupg`, `unzip`, `git`, `jq`, `openssh-client`),
+with `--no-install-recommends`. Pins are **refreshed** when a build breaks on a
+superseded version or when the base image is bumped — the procedure is documented
+in [`docs/dependencies-upgrades.md`](../dependencies-upgrades.md).
+
+Unpinning was explicitly rejected: the bundled tools (Terraform, AWS CLI) are
+already pinned + GPG/checksum-verified, and keeping the OS packages pinned too
+keeps the whole image reproducible and every change explicit in the diff.
+
+**`snapshot.debian.org`** is recorded as the path to make pins *never* break
+(fully reproducible builds); it is deferred to a future ADR/PR rather than
+adopted now, to keep this change minimal.
+
+### Consequences
+
+- Good: reproducible, explicit dependencies; supply-chain integrity preserved.
+- Cost: pins must be refreshed periodically (when Debian supersedes a version) —
+  a manual step today, a candidate for a Renovate custom manager later (#20).
+- Lint: hadolint `DL3008` stays **enforced** (pinning required).
+
+## More information
+
+Pin values are read with:
+
+```bash
+docker run --rm debian:bookworm-slim bash -c \
+  'apt-get update -qq && for p in ca-certificates curl gnupg unzip git jq openssh-client; do \
+     printf "%s=%s\n" "$p" "$(apt-cache policy "$p" | awk "/Candidate:/{print \$2}")"; done'
+```
+
+The bundled-binary verification chain is unchanged
+([`docs/binaries-verifications.md`](../binaries-verifications.md)).
diff --git a/docs/adr/README.md b/docs/adr/README.md
index 7a4a2fd..06fcf1c 100644
--- a/docs/adr/README.md
+++ b/docs/adr/README.md
@@ -58,3 +58,4 @@ Phase 6) will scaffold this automatically.
 | [0007](0007-adopt-entire-checkpoints.md) | Adopt Entire / Checkpoints for agent-session capture | Proposed |
 | [0008](0008-conventional-branch-naming.md) | Conventional branch naming | Accepted |
 | [0009](0009-agent-agnostic-framework.md) | Agent-agnostic framework with a tool-specific adapter layer | Accepted |
+| [0010](0010-apt-package-pinning-strategy.md) | APT package pinning strategy | Accepted |
diff --git a/docs/dependencies-upgrades.md b/docs/dependencies-upgrades.md
index c675333..b2a522d 100644
--- a/docs/dependencies-upgrades.md
+++ b/docs/dependencies-upgrades.md
@@ -3,7 +3,7 @@
 * Supported tools versions:
   * [Report to the doc](https://github.com/zenika-open-source/terraform-aws-cli/tree/master/docs/binaries-verifications.md) to add required security files (stored under `security/`, e.g. `security/hashicorp.asc`) when adding a new supported versions
   * check available **AWS CLI** version on the [project release page](https://github.com/aws/aws-cli/tags)
-  * check available **Terraform CLI** version (keep all minor versions from 0.11) on the [project release page](https://github.com/hashicorp/terraform/releases)
+  * check available **Terraform CLI** version (keep one patch per minor, from 1.0 — see ADR-0004) on the [project release page](https://github.com/hashicorp/terraform/releases)
 * Dockerfile:
   * check **base image** version [on DockerHub](https://hub.docker.com/_/debian?tab=tags&page=1&name=bookworm)
   * check OS package versions on Debian package repository
@@ -16,6 +16,13 @@
     * Available **curl** versions on the [Debian Packages repository](https://packages.debian.org/search?suite=bookworm&arch=any&searchon=names&keywords=curl)
     * Available **gnupg** versions on the [Debian Packages repository](https://packages.debian.org/search?suite=bookworm&arch=any&searchon=names&keywords=gnupg)
     * Available **unzip** versions on the [Debian Packages repository](https://packages.debian.org/search?suite=bookworm&arch=any&searchon=names&keywords=unzip)
+  * OS packages are **pinned to exact versions** in the Dockerfile (see ADR-0010). When a build fails with `apt-get ... exit code 100`, a pin was superseded by Debian — refresh **all** pins to the current candidates, then update the Dockerfile **and** the matching version assertions in [`tests/container-structure-tests.yml.template`](tests/container-structure-tests.yml.template) (e.g. the git/jq/openssh versions):
+
+    ```bash
+    docker run --rm debian:bookworm-slim bash -c \
+      'apt-get update -qq && for p in ca-certificates curl gnupg unzip git jq openssh-client; do \
+         printf "%s=%s\n" "$p" "$(apt-cache policy "$p" | awk "/Candidate:/{print \$2}")"; done'
+    ```
 * Dockerfile tests : update version according to changes in Dockerfile in [tests/container-structure-tests.yml.template](tests/container-structure-tests.yml.template)
 * Github actions:
   * check [runner version](https://github.com/actions/virtual-environments#available-environments)
diff --git a/docs/roadmap.md b/docs/roadmap.md
index 4d60718..f6fe02d 100644
--- a/docs/roadmap.md
+++ b/docs/roadmap.md
@@ -110,6 +110,7 @@ Code) (Phase 2).
 | Dependency bot | **Renovate only** (Dependabot retired) | ADR-0002 |
 | ADR format | MADR (Nygard considered, rejected for simplicity) | ADR-0005 |
 | Terraform deprecation | Drop versions `< 1.0` from `supported_versions.json` | ADR-0004 |
+| APT package pinning | OS utility packages unpinned (stable suite); bundled binaries stay pinned + GPG/checksum verified | ADR-0010 |
 | Rollback policy | No mutation of immutable full tags; consumers re-pin an older tag | `docs/rollback.md` |
 | ADR enforcement | PR-template checkbox + `adr-check.yml` CI gate + CODEOWNERS (no soft-rule-only) | this doc |
 | Branch naming | `type/topic` (Conventional types), `type/phase-N-topic` for phases; no tool names | ADR-0008 |
diff --git a/tests/container-structure-tests.yml.template b/tests/container-structure-tests.yml.template
index 619fc87..fe292c6 100644
--- a/tests/container-structure-tests.yml.template
+++ b/tests/container-structure-tests.yml.template
@@ -11,7 +11,7 @@ commandTests:
   - name: "Check Git version"
     command: "git"
     args: ["--version"]
-    expectedOutput: ["git version 2.39.2"]
+    expectedOutput: ["git version 2.39.5"]
 
   - name: "Check JQ version"
     command: "jq"